1. Field of the Invention
The present invention relates to the installation of pressed pile segments into the earth. More particularly, the present invention relates to methods and apparatus for the measurement of the depth or depth of penetration of the pressed pile during and after it is installed into the earth. The present invention also relates to pile measurement devices and methods.
2. Description of Related Art
There is a type of precast concrete pile used in the underpinning of building foundations comprised of vertically stacked, unconnected, precast concrete segments. These segments are pressed or driven vertically into the soil one at a time until adequate load capacity is obtained. This type of pile is distinctive in that it can be installed with almost no clearance, usually beneath an existing structure.
Although sensible, this pile has several significant disadvantages: (1) the pile segments may not be aligned, other than being stacked on each other, and detrimental misalignment can occur; and (2) independent inspection of the installed pile depth is only possible by providing full-time inspection personnel during installation to monitor the quantity of pile segments used in each pile location. Lack of proper independent inspection of pile depth can lead to inadequate pile penetration, which in highly expansive soil produces an unstable installation subject to continual movements caused by seasonal changes in soil moisture.
During installation, it is often difficult for the installers to fully ascertain whether the pile segments are becoming misaligned. Typically, the workmen during the installation procedure will simply drive one pile segment upon the other with little or no regard to the amount of misalignment that may occur. Often, the number of pile segments that are installed is subject to some disagreement. In certain circumstances, more segments are installed than are necessary or fewer segments are installed than are necessary. Once the segments are installed in the earth, it is difficult to fully determine the number of segments that have been placed beneath the structure, i.e. pile depth.
In the past, various patents have issued relating to the installation of such pressed pile segments. U.S. Pat. No. 5,288,175, issued on Feb. 22, 1994, to D. W. Knight, describes a segmental precast concrete underpinning pile and method using a method of installation where a wire strand aligns the precast segments during installation, provides a means for measurement of pile penetration depth, and continuously reinforces the pile when bonded or anchored upon completion. The depth of pile penetration is inspected by reading the strand marker at the point of installation or may be calculated by measuring the length of the strand remaining from the tip marker and subtracting that length from the calibrated strand length. The depth of pile penetration is inspected when the pile reaches the point of completion. Unfortunately, this is not an entirely reliable technique for measuring pile penetration during the actual installation of the piles. The use of the actual strand as a marker can be a relatively expensive technique for measuring pile depth penetration. Often the laborers will cut the cable in order to finish capping and shimming. The cut portion of the cable is disposed of prior to the engineer""s inspection thereby preventing the engineer from verifying actual pile depth. Since pile depth is often undocumented prior to cutting and disposing of the cable, the actual depth is unverifiable and a matter of opinion and disagreement.
U.S. Pat. No. 5,399,055, issued on Mar. 21, 1995 to E. T. Dutton, Jr., teaches a device and method for leveling and repairing a failed concrete foundation. In this patent, a series of cylindrical pile segments are jacked into the soil while water jetting to a predetermined depth. Reinforcing steel is inserted into the stacked column of cylindrical pile segments. Grount is pumped into the cylindrical pile segments to suitably fix the reinforced steel to the inside of the pile segments. This forms a single shaft pile and does not prevent deflection during installation.
U.S. Pat. No. 6,179,526, issued on Mar. 30, 2001 to Knight et al., teaches a method of forming a pile isolation void including the steps of forming a foundation pile having an enlarged cross-section within a specific localized section and driving the foundation pile a desired distance into the earth so as to form a pile isolation void directly above the enlarged cross-section. The enlarged cross-section can be located at the bottom of the foundation pile or along the length of the foundation pile. The pile isolation void is an annular void extending around the foundation pile above the enlarged cross-section.
U.S. Pat. No. 6,200,070, issued on Mar. 13, 2001 to D. W. Knight, teaches a process of installing piles for supporting a structure upon the earth. This process includes the steps of forming a receptacle in a first pile segment, affixing an end of a strand into the receptacle such that the strand extends outwardly from the first pile segment, sliding a second pile segment onto the strand until the second pile segment contacts a surface of the first pile segment, and driving the second pile segment a desired distance into the earth. The receptacle is formed in the first pile segment while the first pile segment is in the earth. The step of affixing an end of the strand includes the steps of introducing a structural adhesive into a hole formed in the first pile segment, introducing an end of the strand into the hole such that the adhesive contacts the strand and the pile segment, and solidifying the adhesive around the end of the strand such that the end of the strand is rigidly and non-removably secured within the hole in the pile segment.
It is an object of the present invention to provide a method of measuring differential movements between piles and a strand in order to measure deflection of the pile segments during installation.
It is another object of the present invention to provide a method of measuring a depth of a pile which can allow inspectors to determine the pile depth subsequent to installation.
It is a further object of the present invention to provide a method of measuring a depth of a pile which is easy to use, relatively inexpensive and easy to manufacture.
It is still a further object of the present invention to provide a method of measuring a depth n of a pile which is indicative of any misalignment that can occur subsequent to installation.
These and other objects and advantages of the present invention will become apparent from a reading of the attached specification and appended claims.
The present invention is a method of measuring the depth of a pile which supports a structure on the earth comprising the steps of: (1) affixing a flexible strand to a first pile segment; (2) driving the first pile segment a desired distance into the earth such that the flexible strand extends along the length of the first pile segment along an exterior surface thereof; and (3) driving a second pile segment into the earth another desired distance such that the second pile segment resides on a top end of the first pile segment. The flexible strand extends along a length of the second pile segment on an exterior surface of the second pile segment.
Additionally, in the present invention, the method includes the step of driving a plurality of additional pile segments into the earth such that the plurality of additional pile segments reside on an end of the second pile segment opposite the first pile segment. The flexible strand extends along a length of the plurality of additional pile segments on an exterior surface thereof. The first and second pile segments and the plurality of pile segments forms the pile which supports the structure.
An end of the flexible strand is attached to the first pile segment adjacent the bottom end of the first pile segment. Alternatively, an annular member can be inserted into the interior of the first pile segment so as to support a ring member extending outwardly of the exterior surface of the first pile segment at the bottom of the first pile segment. The end of the flexible strand can then be attached to the ring member.
The flexible strand is marked with indicia corresponding to length measurements. More particularly, the flexible strand can correspond to the length of the individual pile segments. The flexible strand is formed of an inelastic material.
The method of the present invention can also include the step of monitoring a length of the flexible strand during the driving of the plurality of pile segments. The step of monitoring can include measuring the rate at which the plurality of pile segments are driven into the earth and then comparing the rate at which the plurality of pile segments are driven into the earth with the rate in which the flexible strand moves into the earth.
The present invention is also a pile length measurement apparatus comprising a plurality of pile segments stacked in end-to-end relationship in the earth, and a flexible strand affixed at one end to the lowermost pile segment. The flexible strand extends along an exterior surface of the plurality of pile segments in surface-to-surface contact with the plurality of pile segments. The flexible strand has indicia formed thereon indicative of length measurements. The flexible strand is formed of an inelastic material.